Bugfix: Show UP_TO_DATE translation status when a translation is manually updated without changes

[seluianova]

Short description

For some historical reasons, when a user saved a translation without content changes, we saved it as a major edit.
Only if there were any other changes on the form, except for the title or content fields, did we save it as a minor edit.

After this change was introduced, we started saving translations without content changes as minor edits.
This introduced the following side effect:
When a user manually updated a machine-translated page without any content changes, it did not change the status from "machine translated" to "up-to-date" (check mark).
Because we defined translation state based on the last major version.

Proposed changes

• When a translation has no content changes, always save it as a minor edit (Previous behavior: only when translation had no content changes BUT other fields on the form were changed, it was saved as a minor edit)
• Adjust the translation_state property: use the last public or draft version to determine the translation state (Previous behavior: the last major version was used)

Side effects

I could not find any, but careful testing is needed.

Faithfulness to issue description and design

There are no intended deviations from the issue and design.

How to test

• Check that the reported issue is not reproduced A previously machine translated page that is outdated will go back to 'machine translated' status after being Updated. #4397
• Check that the previously fixed related issue was not broken again:
  Existing translation outdated after machine translation of unchanged source translation #4254
  After saving a published page as a draft all the existing translations become "outdated" (from draft to publish happens the same) #4284
• Analyze whether any other cases could be affected.

Resolved issues

Fixes: #4397

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Pull Request Review Guidelines

[MizukiTemma]

Looks good 😄

[hannaseithe]

This change looks good to me.

I would suggest to add some tests though, both for the translation_state logic and for the minor_edit flag - just to reduce the regression risk around this rather complex business logic. At the minimum I would suggest a test that checks for the "veraltete machine translated status -> no content update -> UP_TO_DATE state"

[seluianova]

At the minimum I would suggest a test that checks for the "veraltete machine translated status -> no content update -> UP_TO_DATE state"

I agree, I added exactly this test in my another PR: #4399
It just needs to be updated a bit after this PR is merged (currently it checks the previous state - "veraltete machine translated status -> no content update -> up-to-date machine translated")
I will also add a check for minor_edit flag there.

UPD. okay it is not exactly the same, but I would prefer to continue with tests in 4399 anyway, because I also did some test refactoring there to simplify test creation. Would this be fine for you? @hannaseithe